1. Technical Field
The present invention relates to a lens module.
2. Background Art
In the field of image pick-up system, there have been studies recently for developing camera modules for mobile terminals, digital still cameras, camcorders, PC cameras (i.e., image capturing device coupled to PC) and the like. The most important component for acquiring an image in the camera module in relation to the image pick-up system is a lens module having a plurality of lens installed therein for focusing the image.
In the case of a 8 M high-resolution camera, a 4-lens optical system is mainly used for a sensor having the pixel size greater than 1.4 μm, and a 5-lens optical system is used for a sensor having the pixel size of 1.12 μm.
In the 4-lens optical system, the first lens and the second lens are responsible for the entire refractive index of the optical system, and the third lens and the fourth lens are responsible for correcting a field curvature, a distortion, and an aberration that is not corrected by the first lens and the second lens. One of the first lens and the second lens is a Crown series lens, and the other is a Flint series lens to correct a longitudinal chromatic aberration. The second lens usually has a negative refractive index and is made of a flint material.
The most commonly used power arrangement for four lenses constituting the 4-lens optical system is generally a positive-negative-positive-negative arrangement from the first lens.
The 5-lens optical system is implemented by separating the second lens or the third lens of the 4-lens optical system to reduce the refractive angle of each lens and to optimize the performance of each field.
The related art of the present invention is disclosed in Korea Patent Publication No. 10-2012-0039075 (IMAGE PICKUP LENS, IMAGE PICKUP APPARATUS AND PORTABLE TERMINAL; laid open on Apr. 25, 2012).